Quad Power Supply For Hybrid Amplifier

This power supply was designed for use with the Simple hybrid amp` published elsewhere in this issue. It is of course suitable for use in other applications as well. We`ve used a cascade generator for the 170 V, a switch mode supply for the 16 V, a series regulator for the 12 V and a separate transformer for the 6. 3 V filament supply. We`ve chosen

an LT1074CT (IC1) for the regulator, which means that the circuit can be built with relatively standard components and will have a high efficiency. The power loss is less with this device compared to a linear voltage regulator. This allows us to use a higher transformer voltage and a smaller cascade section to generate the 170 V (which is required for the SRPP stage in the amplifier). The lower input current also results in smaller losses in the bridge rectifier (D1 to D4). A standard 12 V regulator (IC2) turns the 16 V into a stabilised voltage for the buffer stage. When an ECC83 (12AX7) is used in the hybrid amp we could use this 12 V to power the filaments in the valve as well, although we really need 12. 6 V. The current taken by the valve is about 150 mA, which means that the 12 V regulator needs to be fitted with a heatsink. This can be a small version of an SK129 heatsink from Fischer (38. 1 mm, 6. 5 K/W). To increase the voltage by 0. 6 V we`ve added diode D7 to the ground connection of the regulator. If an output voltage of 12 V is required you should close JP1, which shorts D7. IC1 and D5 require a little more cooling and for this the 63. 5 mm version of the SK129 will suffice (4. 5 K/W). Both components can be mounted on opposite sides of the heatsink. You have to make sure that they are electrically isolated from each other and the heatsink! You should take a look at the website of Linear Technology ( and take...

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